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RAID 5 and unrecoverable read errors versus storage spaces

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Omega Destroyer

Member
Joined
Sep 27, 2002
Location
Alberta
I'm setting up a new RAID array and I was planning on going RAID 1, primarily because of I've read in many places that unrecoverable read errors can occur during a rebuild of RAID 5 arrays. These errors apparently cause the rebuild to fail.

Just wondering if the Windows 8.1 "parity" setting in storage spaces in vulnerable to the same issue, or does it work in a different manner than RAID5.

Ideally I would like to choose Parity, since performance is not an issue and I could use the extra space, but I don't want to run into unrecoverable bits during rebuilds.

Any insights?
 
URE's are definitely a problem in RAID 5 recoveries and the better the drive's rating for it say 1 in 1x10^16 or 1 in 1x10^17 the less likely you are to encounter a URE. The larger the disks are and the lower the rating say like 1 in 1x10^14 the more like you are to have a rebuild failure.

The operating system itself does not provide parity, thats done by the RAID structure.

In RAID 1 you are totally fault tolerant but at the cost of double the amount of drives and no extra read/write speeds. RAID 5 has great Read speeds and the same if not worse write speeds and is 1 drive fault tolerant because of the distributed parity. The next level is RAID 6 where you have two disks which the parity is distributed to instead of 1 in RAID 5.

Generally your more expensive enterprise level hard drives will have the lower URE ratings and have special built in error recovery controls to prevent a drive from being dropped from a RAID array if it takes too long to respond.
 
Can you give us more detail about what you are planing. How much space you are looking for, drives you are planing on using, etc...
 
Sorry, I should have worded my question a bit better. I understand the risks of RAID 5, which is why I wanted to avoid it since I will be using
4x seagate 4 TB NAS drives.
My question is whether the new "Storage spaces" feature of windows 8 and windows server 2012 suffers from the same problems as large RAID 5 arrays.

"Storage spaces" allows you to mirror drives (similar to RAID1 but allows the use of ReFS instead of NTFS which adds additional resiliency). It also allows you to set up the drives in "parity" mode, but it's not clear exactly what that is. The capacity is N-1 like RAID5, but I was wondering if anyone knew about the technical details of windows "storage spaces" parity mode, and if a URE will cause a rebuild failure.
 
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I dont know about the software RAID from windows 8 (which I wouldn't use).

http://www.raid-failure.com/raid5-failure.aspx

Check out the above link. The drives you are talking about are RAID specific but only have a 1 in 1x10^14 rating for URE's. So by using that calculator for a 4 x 4TB (4096GB) array in RAID 5 you could have a 27% probability of success in rebuilding the array. That probability would increase to 87.7% if you went with one of Seagates Constellation drives which boast a 1 in 1x10^15 rating.

The site also notes that the calculated probabilities are not set in stone because of some reasons mentioned here... http://www.raidtips.com/raid5-ure.aspx
 
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